Process of bleaching fatty acids



Patented 17, 1929 STATES nnmi Goblin, or vnsrnn Anna, NEAR OSLO, NORWAY EROCESS OF BLEACHING FATTY ACIDS I No Drawing. Application filed February 11, 1926, Serial No. 87,677, and in Norway January 29, 1925.

substances, albumen and other proteids.

Crude fatty acids of this character are obtained as by-products or as primary products in several industries. Thus when crude whale oil or fish oils containing free fattyacids are neutralized with alkali and the resulting mass of crude soaps (soap stock) is decomposed by means of acids a crude fatty acid product results which is entirely free from precipitable proteids. The crude fatty acids obtained by most of the usual fat de composition processes are also of this character.

V hen fats or oils are to be decomposed to obtain fatty acids and glycerine according to the usual methods the satisfactory course of the process as well as the output will be greatly dependent upon the degree of purity of the treated raw materials. The fats or oils to be subjected to the decomposition treatment are therefore in actual manufacturing practice always subjected to a treatment with sulphuric acid to precipitate impurities before the decomposition operation is commenced. For this reason the resulting fatty acids will be practically free from such impurities which are precipitated by sulphuric acid. lit is therefore not possible to bleach fatty acid'materials of this type by the known addition of albumen-coagulating substances (alum, tannine dilute mineral acids etc.) forming separable deposits enclosing the discoloring matter.

For this reason the bleaching of strongly colored fatty acids is at present usually. effected by distillation in order to obtain satisfactory and reliable results. The temperatures required in the fatty acid distillation is however high (about 250 C. and higher) and on the other hand the socalled oxy-fatty acids are not distillable and this method is therefore not. suitable for the treatment of materials sensitive to high temperatures and containing considerable proportions of oxyfatty acids. Further this method necessitutes the useof compllcated and expensive apparatus, whiclron account of the high temperatures of operation do not last long.

Crude fatty acids containing a large proportion of strongly unsaturated fatty acids and more particularly fatty acids from whale and fish oils give a low output when subjected to purification by distillation and this is more particularly so when the crude fatty acids contain substantial proportions of oxidized fatty acids. 1

Thus when crude fatty acids obtained by decomposing soap stock from low grade whale oil are subjectedto distillation an output of only 7580 per cent bleached product (distilled fatty acids) is usual.

The present invention has for its object a process of bleachingand deodorizing fatty acids by which such, results can be attained without the use of distillation processes.

The invention is based upon the discovery that When fatty acids of a marine origin, diluted with a volatile solvent are reacted upon with strong sulphuric acid, sulphonation products are formed which are insoluble in the fatty acid solution and on being deposited enclose the coloring substances and carry them down. When the precipitate has been separated from the solution a colorless liquid remains. This is a surprising effect when it is considered that oils of a marine origin become strongly and permanently discolored byvthe action of concentrated sulphuric acid.

Tn accordance with this observation the present process comprises the steps of dissolving the crude fatty acids of the character referred to above in a volatile solvent, reacting upon the solution with strong sulphuric acid to form a small proportion of sulphonated fatty acid, "separating undissolved matter comprising undissolved sulphonated fatty acids and coloring substance from the solution and expelling the volatile solvent from the remaining non-volatile matter. The sulphonation treatment is suitably effected at a low temperature. When operating at about room temperature the reaction will usually be completed in the course of six to seven ours.

The Various steps of the processwill of course have to be modified within wide limits depending upon the character of the treated materials.

As examples of suitable solvents are to be mentioned benzin, benzol, carbon bisulphide, chlorine substituted hydro carbons, for example, tetrachlorethane and carbon tetrachloride and the like. The sulphonation of the dissolved fatty acids is effected by means of sulphuric acid in such a quantity and un der such other conditions of operation that only quite small quantities of sulphonated fatty acids are produced.

The process can suitably be carried into effect in the manner described below.

The raw material (which for example can I be a commcrical fatty acid containing proportions of undecomposed glycerides) 1s dlssolved in suitable proportionsin the solvent (for example benzin) and is at 15-20 C. supplied with a certain quantity of strong sulphuric acid while being violently agitated:

Example: 100 kilogrammes of crude fatty acid obtained from low grade whale blubber oil, and being of a dark brown color and practically free from precipitable proteids were dissolved in 120 kilogrammes of henzine. To this solution, maintained at a temperature of between 15 and 20 (1., 5 kilogrammes of sulphuric acid of 92 per cent were gradually supplied in the course-of about one hour and a half while vigorously stirring the solution.

The solution was left standing about seven hours (at 1520 C.),Where,by a black deposit was formed on the bottom of the container employed, below a clear and colorless liquid. This black deposit consists of sulphuric acid together with a small proportion of sulphonated fatty acid enclosing the coloring matter contained in the initial crude fatty acids.

The clear liquid was drawn off from the black layer into another vessel, where it was washed With water. The volatile solvent (benzine) was thereupon expelled from the bleached fatty acids by evaporation, so as to be made available for repeated use. The total weight of the resulting bleached fatty acid was about 97 per cent.

'It may sometimes be'desirable to combine I the bleaching as above described with a treatment with fullersearth and other bleaching earth. The treatment with such bleaching earths is then preferably effected subsequent to the sulphonation treatment by adding the bleaching earth to the solution after its having been drawn off from the black bottom upon it is separated from the solution by settling or filtration. The further treatment may be as described in the above example.

The bleaching is accompanied by a notable deodorizing, the acid in part decomposing ration.

Claims:

1. Process of bleaching crude fatty acids of a marine origin practically free from precipitable proteids comprising the steps of dissolving the crude fatty acids in a volatile solvent, reacting upon the dissolved fatty acids with strong sulphuric acid for such a period of time and under such conditions of temperature as to produce a small proportion of sulphonated fatty acids, separating undissolved matter from the solution of fatty acids, and expelling the volatile solvent from the bleached fatty acids.

2. Process according to claim 1 in which the solution of fatty acid in volatile solvent is reacted upon with sulphuric acid at a temperature of between 15 and 20 C.

'3. Process according to claim 1 in which the solution of fatty acids in volatile solvent is repeatedly washed with water between the steps of removing the undissolved matter and of expelling the Volatile solvent.

In testimony that I claim the foregoing as my invention, I have signed my name.

ARNE GODAL. 

